I agree with this. I remember when Gnome 3 came out, there were a lot of legitimate complaints that were handwaved away by the developers as "doesn't work well on a mobile interface", despite Gnome having approximately zero install cases onto anything mobile. AFAICT that probably hasn't changed, all these years later.
I don’t know. I just started distributing a gtk app and I’ve already gotten two issue reports from people using it on mobile experiencing usability problems. Not something I thought I’d have to worry about when I started but I guess they are out there.